Remove mojo::String.

device/geolocation/geolocation_service_impl.cc

Index: device/geolocation/geolocation_service_impl.cc
diff --git a/device/geolocation/geolocation_service_impl.cc b/device/geolocation/geolocation_service_impl.cc
index bbcbbd54c5ce1903acbe3e5e02230fabec194cdd..a56b6d83427325b8cc59bcf0556bcf4dca7b678f 100644
--- a/device/geolocation/geolocation_service_impl.cc
+++ b/device/geolocation/geolocation_service_impl.cc
@@ -78,7 +78,7 @@ GeolocationServiceImpl::~GeolocationServiceImpl() {
     if (!current_position_.valid) {
       current_position_.error_code = mojom::Geoposition::ErrorCode(
           GEOPOSITION_ERROR_CODE_POSITION_UNAVAILABLE);
-      current_position_.error_message = mojo::String("");
+      current_position_.error_message.clear();
     }
     ReportCurrentPosition();
   }